Poly(ester-amide)s (PEAs) are polymers synthesized from non-toxic amino acids, diols and dicarboxylic acids and are composed of both ester and amide blocks. They have been widely studied because they combine the favorable properties of both polyesters and polyamides, i.e., they possess not only good biodegradability but also good mechanical and processing properties, e.g., thermal stability, tensile strength and modulus. Amino acids, due to their abundant availability from natural sources and the potential biodegradability of their derivatives under certain enzymatic catalyzed conditions, have often been chosen as the source for the amine group of the biodegradable poly(ester-amide)s. It has also been reported that the inclusion of phenylalanine in the backbone of the PEAs can enhance their biodegradability in the presence of chymotrypsin.
All PEAs reported in the literature contain saturated backbone bridging structures. See, for example, U.S. Pat. No. 6,503,538 B1. This means that the PEAs synthesized before now, have to be modified before other chemicals can be reacted with them.